in this video we're going to focus on balancing Chemical Equations so let's get right into it let's start with a combustion reaction so here we have propane C3 h8 plus oxygen gas and that's going to produce carbon dioxide and water now whenever you want to balance a chemical reaction your goal is to make sure that the atoms are equal on both sides of the reaction for this particular combustion reaction we want to balance the carbon atoms first then the hydrogens and then the oxygen we'll save that for last so notice that we have three carbon atoms on the left side that means we need three carbon atoms on the right side and here we only have one carbon atom in CO2 so what we need to do is put a three in front of carbon dioxide so now we have three carbon atoms on both sides so let's move on to the hydrogen atoms notice that we have eight hydrogen atoms on the left side and the only molecule that has hydrogen is water what number do we need to put in front of H2O 8 / 2 is what number 8 / 2 is four so you need to put a four in front of H2O so you have eight hydrogen atoms on both sides now let's move on to the oxygen atoms what is the total number of oxygen atoms on the right side notice that we have six oxygen atoms in the three CO2 molecules if you multiply 3x two you're going to get six and we have four oxygen atoms in the four water molecules if you don't see a subscript it's a one 4 * 1 is 4 so we have a total of 10 oxygen atoms on the right side so what number do we need to put in front of o2 so that we have 10 oxygen atoms on both sides 10 / 2 is five so we need to put a five in front of o2 so everything is balanced we have three carbon atoms on both sides eight hydrogen atoms and a total of 10 oxygen atoms on both sides and that's really what you need to do to balance an equation just make sure the number of atoms on both sides are equal so now let's try another example butane C4 h10 plus O2 produces CO2 and water go ahead and balance this reaction so just like the last example let's balance the carbon atoms first we have four carbon atoms on the left side so four / 1 is four we need to put a four in front of CO2 to make it work now let's move on to the hydrogen atoms notice that we have 10 hydrogen atoms on the left side 10 / 2 is 5 so we need to put a five in front of H2O so that we can have a total of 10 hydrogen atoms on both sides now how many oxygen atoms do we have on the right side so in four CO2 molecules we have a total of eight oxygen atoms 4 * 2 is 8 in the 5 H2 molecules we have a total of 5 * 1 oxygen atoms so just five so we have a total of 13 and if we try to balance the equation we're going to have a fraction 13 / 2 is 13 over two right now this reaction is balanced but we need whole numbers we don't want fractions so all we need to do at this point is we simply need to multiply the equation by two and then it's going to be balanced so it's going to be 2 C4 h10 plus 13 O2 we're going to have 8 CO2 molecules and 10 water molecules now let's make sure our answers are correct notice that we have eight carbon atoms on both sides 2 * 4 is 8 and we also have 20 hydrogen atoms 2 * 10 is 20 and let's check the total number of oxygen atoms 13 * 2 is 26 so we have 26 oxygen atoms on the left side 8 * 2 is 16 10 * 1 is 10 so 16 + 10 that's 16 oxygen atoms so this equation is balanced let's try this one aluminum plus hydrochloric acid produces aluminum chloride and hydrogen gas so feel free to pause the video and work out this problem let's begin by balancing the number of chlorine atoms we have three chlorine atoms on the right side and only one on the left side so our natural inclination is to put a three in front of htl the only issue with that is we have an odd number of hydrogen atoms on the left side but an even number of hydrogen atoms on the right side whenever you come across this even odd situation you can Rectify this situation by simply multiplying everything by two so instead of putting three in front of HC let's put a six so we have six chlorine atoms that means that we need to put a two in front of alcl 3 because 6 / 3 is 2 so we have six chlorine atoms on both sides now we have six hydrogen atoms on the left but only two on the right so what number do we need in front of H2 6 / two is three so we need to put a three in front of H2 so we have six hydrogen atoms on both sides now we have two aluminum atoms on the right side but only one on the left side so we need to put a two in front of Al so now the reaction is balanced this is the answer so here's another example gallium plus copper bromide produces gum bro and copper metal go ahead and balance the reaction so notice that we have two bromine atoms on the left side and three on the right side so we have that even odd situation the least common multiple of two and three is six so what you want to do is you want to try to get six bromine atoms on both sides 6 / 2 is three so let's put a three in front of copper bromide 6 / 3 is 2 so we'll put a two here so notice that we have six bromine atoms on both sides of the equation so now at this point we just got to balance the other atoms we have three copper atoms on the left so we need to put a three in front of Cu and we have two gallium atoms on the right side so we need to put a two in front of GA and reaction is balance that's all you got to do for this example try this one I2 + F2 produces if7 go ahead and balance the reaction so here we have the even odd situation we have two floring atoms on the left seven on the right the least common multiple of two and seven is 14 so that tells us that we want to try to get 14 Florine atoms on both sides 14 / 7 is 2 and 14 / 2 is 7 so notice that the Florine atoms are balanced and we already have two iodine atoms on the right side two on the left so this reaction is balanced you can put a one here if you want but you don't have to but that's all you got to do for that example try this one SO2 sulfur dioxide plus oxygen gas produces sulfur trioxide go ahead and balance the V oxygen so we have a total of four oxygen atoms on the left side and three on the right side what can we do in this particular example if we make this a half notice that the reaction will be balanced we have two oxygen atoms in SO2 a half * 2 is 1 the twoos cancel 2 + 1 is 3 so it's balanced but we don't have any whole numbers so what we need to do is multiply the equation by two so 2 SO2 2 * a half we said it's 1 so 1 O2 produces two3 molecules notice that it's balanced at this point so we have two sulfur atoms on both sides on the right side we have six oxygen atoms 2 * 3 is6 on the left side we have four oxygen atoms from the two SO2 molecules plus another two oxygen atoms and so that adds six so we can see that we have the same number of oxygen atoms on both sides so this is the answer this is the balanced reaction consider this reaction sodium metal plus Elemental sulfur produces sodium sulfide let's say if we have sulfur in its S8 form how would you balance this reaction what would you do so we have eight sulfur atoms on the left but only one on the right so that tells us that we need to put a eight on the right side since 8 * 1 is 8 so we have eight sulfur atoms on both sides how many sodium atoms do we have on the left side 8 * 2 is 16 I meant to say on the right side not on the left side so we have 16 sodium atoms on the right side that tells us that we need to put a 16 in front of Na and now the reaction is balanced so the coefficients are 161 and eight try this one sodium phosphate na3 po4 plus magnesium chloride produces sodium chloride and magnesium phosphate go ahead and balance this reaction this is called a double replacement reaction and for these types of reactions you don't always want to balance each atom individually it might be easier to view phosphate P4 as an entire unit it's going to make it a lot easier notice that we have one phosphate unit on the left but we have two phosphate units on the right side if you see it that way it's going to be easier to balance it let's put a two in front of the left side so we have two P4 units now notice that we have six sodium atoms on the left side 2 * 3 is six so we have six sodium atoms therefore what number do we need to put in front of NaCl so we got to put a six in front of NaCl so we have six sodium atoms on both sides and two phosphate units or P4 units on each side now notice that we have three magnesium atoms on the right side but we have none on the left side so we got to put a three in front of mg so we have three magnesium atoms on both sides now notice that we have six chlorine atoms on the right side and six on the left 3 * 2 is six so this reaction is balance here's another double replacement reaction that you could work on potassium sulfate k204 plus aluminum chloride al3 produces potassium chloride and aluminum sulfate al2 s so43 go ahead and balance the reaction so let's start with the sulfate units that's the S so4 units notice that we have one s so4 unit on the right but three on the left so that tells us that we need to put a three in front of k2so4 so we have three sulfate units on each side notice that we have two aluminum atoms on the right side so we need to put a two in front of Al cl3 so we got two aluminum atoms on both sides once we do that notice that we have six chlorine atoms on the left side so we got to put a six in front of KCl once we do that we have six potassium atoms and 3 * 2 is six so everything is balanced at this point so this is the answer the coefficients are three 2 six and one let's try another example ammonia plus oxygen gas produces nitrogen monoxide and water so what can we do to balance this reaction so it appears as if the nitrogen atoms are balanced we have one nitrogen atom on both sides the hydrogen atoms are not balanced we should save oxygen for last because we can always modify since we have O2 by itself as a Pure Element so let's not worry about oxygen for now let's start by balancing the hydrogen atoms so we have an odd number of hydrogen atoms on the left and an even number on the right side so let's double the number of hydrogen atoms so we have six on the left side which means we need three in front of water so we now have six hydrogen atoms on both sides so now at this point we have two nitrogen atoms on the left only one on the right so we need to put a two in front of n so we have two nitrogen atoms on each side so now let's look at oxygen we have two oxygen atoms in the two n molecules and three from 3 H2O so we have a total of five which is odd and here if we balance it now it's going to be five divided by this number two so as a fraction is 5 over two even though the reaction is balance we don't want to leave it like this we need to multiply everything by two so it's going to be 4 NH H3 5 over 2 * 2 the twos will cancel and so it's going to be 502 and four n o plus 6 H2O molecules so now the reaction is balanced so if we check our work we can see that we have four nitrogen atoms on both sides here we have 4 * 3 which is 12 6 * 2 is 12 so we have 12 hydrogen atoms on each side here this is uh 4 * 1 that's 4 6 * 1 is six so we have a total of 10 oxygen atoms on the right side 5 and two is also 10 so everything is balanced try another combustion reaction ethanol plus oxygen gas produces carbon dioxide and water CO2 and water are always the products for a combustion reaction so let's begin let's start by balancing the number of carbon atoms notice that we have two carbon atoms on the left so we need to put a two in front of CO2 now how many hydrogen atoms do we have on the left side we have 5 + 1 so we have a total of six so what number do we need to put in front of H2O 6 / two is three so we need three water molecules so that we have six hydrogen atoms on both Ides so now let's move on to the oxygen atoms in the two CO2 molecules 2 * 2 is four so we have four oxygen atoms there 3 * 1 is three so we have three oxygens in three water molecules notice that we have an oxygen in ethanol so we need a total of seven oxygen atoms on both sides so what number goes here let's call it X so 1 + x = 4 + 3 4 + 3 is 7 1 plus what number is s that missing number is six 7 - 1 is 6 so we need six oxygen atoms from O2 6 / 2 is three so we got to put a three in front of o two so now everything is balanced we have two carbon atoms on both sides six hydrogen atoms and a total of seven 3 * 2 is 6 + 1 that gives us seven 2 and two is four 3 and 1 is three four and three is seven so everything is equal and reaction is now balanced so that is it for this video thanks for watching and have a great day